Terbinafine belongs to which antifungal drug class?

• A. Allylamines
• B. Azoles
• C. Echinocandins
• D. Polyenes

Answer: (A)

The question tests recognizing antifungal drug classes by mechanism of action. Terbinafine is an allylamine, because it inhibits squalene epoxidase, an early enzyme in ergosterol synthesis. This leads to accumulation of toxic squalene and depletion of ergosterol, disrupting the fungal cell membrane. This mechanism is distinct from other classes: azoles block the lanosterol 14-α-demethylase step, echinocandins inhibit beta-1,3-glucan synthesis in the cell wall, and polyenes bind ergosterol to form membrane pores. Clinically, terbinafine is especially effective against dermatophyte infections (like tinea and onychomycosis) and is used in topical and oral forms, reflecting its strong activity against these fungi and its particular pharmacokinetic profile.